Parameters

The property map that stores the position of each vertex. The type
PositionMap must be a model of Lvalue Property
Map such that the vertex descriptor type of Graph is
convertible to its key type. Its value type must be
Topology::point_type, representing the coordinates of the vertex.

IN: const Topology& space

The topology used to lay out the vertices. This parameter describes both the
size and shape of the layout area and provides a random number generator used
to create random positions within the space. Topologies are described in
more detail (with a list of BGL-provided topologies) in separate documentation.